arXiv subjects

Sabyasachi Pal

Publications and source records attributed to Sabyasachi Pal.

At least 37 records · Page 2Linked to original sources

arXiv2024

First Identification and Chemical Modeling of New Thiol ($-$SH) Bearing Molecule in the Interstellar Medium: Dithioformic Acid

The study of complex organic molecules containing thiol ($-$SH) groups is essential in interstellar media because $-$SH plays an important role in the polymerization of amino acids (R-CH(NH$_{2}$)-COOH). Some quantum chemical studies have shown that there is a high chance of detecting the emission lines of dithioformic acid (HC(S)SH) in the highly dense and warm-inner regions of hot molecular cores and hot corinos. Therefore, we attempted to search for the emission lines of HC(S)SH toward the highly dense hot corino object NGC 1333 IRAS 4A using the Atacama Large Millimeter/Submillimeter Array (ALMA) band 7. We present the first detection of the rotational emission lines of the trans-conformer of dithioformic acid (t-HC(S)SH) toward the NGC 1333 IRAS 4A2. The column density and excitation temperature of the t-HC(S)SH toward NGC 1333 IRAS 4A2 are (2.63$\pm$0.32)$\times$10$^{15}$ cm$^{-2}$ and 255$\pm$32 K, respectively. The fractional abundance of t-HC(S)SH with respect to H$_{2}$ is (2.53$\pm$0.68)$\times$10$^{-9}$. The column density ratio of t-HC(S)SH and t-HCOOH toward NGC 1333 IRAS 4A2 is 0.36$\pm$0.02. To understand the possible formation pathways of HC(S)SH, we computed a two-phase warm-up chemical model abundance of HC(S)SH using the gas-grain chemical code UCLCHEM. After chemical modeling, we claim that HC(S)SH is formed in NGC 1333 IRAS 4A2 via barrierless radical--radical reactions between CSSH and H on the grain surfaces.

astro-ph.GA↗

arXiv2024

Ten years of searching for relics of AGN jet feedback through RAD@home citizen science

Understanding the evolution of galaxies cannot exclude the important role played by the central supermassive black hole and the circumgalactic medium (CGM). Simulations have strongly suggested the negative feedback of AGN Jet/wind/outflows on the ISM/CGM of a galaxy leading to the eventual decline of star formation. However, no "smoking gun" evidence exists so far where relics of feedback, observed in any band, are consistent with the time scale of a major decline in star formation, in any sample of galaxies. Relics of any AGN-driven outflows will be observed as a faint and fuzzy structure which may be difficult to characterise by automated algorithms but trained citizen scientists can possibly perform better through their intuitive vision with additional heterogeneous data available anywhere on the Internet. RAD@home, launched on 15th April 2013, is not only the first Indian Citizen Science Research (CSR) platform in astronomy but also the only CSR publishing discoveries using any Indian telescope. We briefly report 11 CSR discoveries collected over the last eleven years. While searching for such relics we have spotted cases of offset relic lobes from elliptical and spiral, episodic radio galaxies with overlapping lobes as the host galaxy is in motion, large diffuse spiral-shaped emission, cases of jet-galaxy interaction, kinks and burls on the jets, a collimated synchrotron thread etc. Such exotic sources push the boundaries of our understanding of classical Seyferts and radio galaxies with jets and the process of discovery prepares the next generation for science with the upgraded GMRT and Square Kilometre Array Observatory (SKAO).

astro-ph.GA↗

arXiv2024

Confirmation of interstellar phosphine towards asymptotic giant branch star IRC+10216

Phosphorus (P) is an important element for the chemical evolution of galaxies and many kinds of biochemical reactions. Phosphorus is one of the crucial chemical compounds in the formation of life on our planet. In an interstellar medium, phosphine (PH$_{3}$) is a crucial biomolecule that plays a major role in understanding the chemistry of phosphorus-bearing molecules, particularly phosphorus nitride (PN) and phosphorus monoxide (PO), in the gas phase or interstellar grains. We present the first confirmed detection of phosphine (PH$_{3}$) in the asymptotic giant branch (AGB) carbon-rich star IRC+10216 using the Atacama Large Millimeter/Submillimeter Array (ALMA) band 6. We detect the $J$ = 1$_{0}$$-$0$_{0}$ rotational transition line of PH$_{3}$ with a signal-to-noise ratio (SNR) of $\geq$3.5$σ$. This is the first confirmed detection of phosphine (PH$_{3}$) in the ISM. Based on LTE spectral modelling, the column density of PH$_{3}$ is (3.15$\pm$0.20)$\times$10$^{15}$ cm$^{-2}$ at an excitation temperature of 52$\pm$5 K. The fractional abundance of PH$_{3}$ with respect to H$_{2}$ is (8.29$\pm$1.37)$\times$10$^{-8}$. We also discuss the possible formation pathways of PH$_{3}$ and we claim that PH$_{3}$ may be created via the hydrogenation of PH$_{2}$ on the grain surface of IRC+10216.

astro-ph.GA↗

arXiv2024

Probing the energy and luminosity-dependent spectro-timing properties of RX J0440.9+4431 with AstroSat

The Be/X-ray binary pulsar RX J0440.9+4431 went through a giant outburst in December 2022 with a peak flux of $\sim$2.3 Crab in 15--50 keV. We studied the broad-band timing and spectral properties of RX J0440.9+4431 using four $AstroSat$ observations, where the source transited between subcritical and supercritical accretion regimes. Pulsations were detected significantly above 100 keV. The pulse profiles were found to be highly luminosity- and energy-dependent. A significant evolution in the pulse profile shape near the peak of the outburst indicates a possible change in the accretion mode and beaming patterns of RX J0440.9+4431. The rms pulsed fraction was luminosity- and energy-dependent, with a concave-like feature around 20--30 keV. The depth of this feature varied with luminosity, indicating changes in the accretion column height and proportion of reflected photons. The broad-band continuum spectra were best fitted with a two-component Comptonization model with a blackbody component or a two-blackbody component model with a thermal Comptonization component. A quasi-periodic oscillation at 60 mHz was detected at a luminosity of $2.6 \times 10^{37}$ erg s$^{-1}$, which evolved into 42 mHz at $1.5 \times 10^{37}$ erg s$^{-1}$. The QPO rms were found to be energy dependent with an overall increasing trend with energy. For the first time, we found the QPO frequency varying with photon energy in an X-ray pulsar, which poses a challenge in explaining the QPO with current models such as the Keplarian and beat frequency model. Hence, more physically motivated models are required to understand the physical mechanism behind the mHz QPOs.

astro-ph.HE↗

arXiv2024

ALMA detection of hydrogen cyanide (HCN) in the atmosphere of Saturn

In the planetary atmosphere, hydrogen cyanide (HCN) is an important nitrogen (N)-bearing molecule that plays a key role in the formation of several biomolecules via chain reactions. The presence of HCN characterizes the stratospheric composition of the solar gas planets and exoplanets. For several years, many observations have failed to identify the rotational and vibrational emission lines of HCN from the atmosphere of Saturn using ground- and space-based radio telescopes. We present the successful detection of the rotational emission line of HCN from the atmosphere of Saturn using the Atacama Large Millimeter/Submillimeter Array (ALMA) band 7. We detected the J = 4$-$3 transition line of the HCN from the eastern and western limbs of Saturn with $\geq5σ$ statistical significance. The derived abundances of HCN in the western and eastern limbs are 6.19 ppb and 2.90 ppb, respectively. We claim that HCN is formed in the atmosphere of Saturn via the photolysis of methane (CH$_{4}$) and ammonia (NH$_{3}$).

astro-ph.EP↗

arXiv2024

Detection of antifreeze molecule ethylene glycol in the hot molecular core G358.93$-$0.03 MM1

The identification of complex prebiotic molecules using millimeter and submillimeter telescopes allows us to understand how the basic building blocks of life are formed in the universe. In the interstellar medium (ISM), ethylene glycol ((CH$_{2}$OH)$_{2}$) is the simplest sugar alcohol molecule, and it is the reduced alcohol of the simplest sugar-like molecule, glycolaldehyde (CH$_{2}$OHCHO). We present the first detection of the rotational emission lines of $aGg^{\prime}$ conformer of ethylene glycol ((CH$_{2}$OH)$_{2}$) towards the hot molecular core G358.93$-$0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The estimated column density of $aGg^{\prime}$-(CH$_{2}$OH)$_{2}$ towards the G358.93$-$0.03 MM1 is (4.5$\pm$0.1)$\times$10$^{16}$ cm$^{-2}$ with an excitation temperature of 155$\pm$35 K. The abundance of $aGg^{\prime}$-(CH$_{2}$OH)$_{2}$ with respect to H$_{2}$ is (1.4$\pm$0.5)$\times$10$^{-8}$. Similarly, the abundances of $aGg^{\prime}$-(CH$_{2}$OH)$_{2}$ with respect to CH$_{2}$OHCHO and CH$_{3}$OH are 3.1$\pm$0.5 and (6.1$\pm$0.3)$\times$10$^{-3}$. We compare the estimated abundance of $aGg^{\prime}$-(CH$_{2}$OH)$_{2}$ with the existing three-phase warm-up chemical model abundance of (CH$_{2}$OH)$_{2}$, and we notice the observed abundance and modelled abundance are nearly similar. We discuss the possible formation pathways of $aGg^{\prime}$-(CH$_{2}$OH)$_{2}$ towards the hot molecular cores, and we find that $aGg^{\prime}$-(CH$_{2}$OH)$_{2}$ is probably created via the recombination of two CH$_{2}$OH radicals on the grain surface of G358.93$-$0.03 MM1.

astro-ph.GA↗

arXiv2024

J0011+3217: A peculiar radio galaxy with a one-sided secondary lobe and misaligned giant primary lobes

From the LOFAR Two-metre Sky Survey second data release (LoTSS DR2) at 144 MHz, we identified a peculiar radio galaxy, J0011+3217. It has a large, one-sided diffuse secondary wing that stretches up to 0.85 Mpc (roughly 85\% of the size of the primary lobe). The linear size of the primary lobe of the galaxy is 0.99 Mpc. This peculiar source is a giant radio galaxy with a misaligned primary lobe. There is an optical galaxy 16 kpc (7 arcsec) from the host active galactic nucleus of J0011+3217. J0011+3217 has a radio luminosity of $1.65\times 10^{26}$ W Hz$^{-1}$ at 144 MHz with a spectral index of $-0.80$ between 144 and 607 MHz. J0011+3217 is located 1.2 Mpc from the centre of the Abell 7 cluster. The Abell 7 cluster has a redshift of 0.104 and a mass ($M_{500}$) of 3.71 $\times 10^{14}$ M$_\odot$. The cluster is associated with strong X-ray emission. We studied the X-ray emission around the cluster and from the region surrounding J0011+3217 using an XMM-Newton image of J0011+3217, and we analysed the velocity structure and spatial distribution of galaxies in the cluster, showing that J0011+3217 inhabits an offset group of galaxies that are moving with respect to Abell 7. The off-axis distortion, or bending, of the primary lobe of J0011+3217 in the outer edges has a strong effect on the relative motion of the surrounding medium; this in turn causes the bending of the jets in the opposite direction of the cluster (like wide-angle tailed sources). We suggest that the morphology of J0011+3217 is influenced by ram pressure created by the Abell 7 cluster, highlighting the complex interactions between the source and the surrounding cluster environment.

astro-ph.GA↗

arXiv2024

Observation of Complex Organic Molecules Containing Peptide-like Bonds Toward Hot Core G358.93$-$0.03 MM1

In star formation regions, the complex organic molecules (COMs) that contain peptide bonds ($-$NH$-$C(=O)$-$) play a major role in the metabolic process because $-$NH$-$C(=O)$-$ is connected to amino acids (R-CHNH$_{2}$$-$COOH). Over the past few decades, many COMs containing peptide-like bonds have been detected in hot molecular cores (HMCs), hot corinos, and cold molecular clouds, however, their prebiotic chemistry is poorly understood. We present the first detection of the rotational emission lines of formamide (NH$_{2}$CHO) and isocyanic acid (HNCO), which contain peptide-like bonds toward the chemically rich HMC G358.93$-$0.03 MM1, using high-resolution and high-sensitivity Atacama Large Millimeter/submillimeter Array bands 6 and 7. We estimate that the column densities of NH$_{2}$CHO and HNCO toward G358.93$-$0.03 MM1 are (2.80$\pm$0.29)$\times$10$^{15}$ cm$^{-2}$ and (1.80$\pm$0.42)$\times$10$^{16}$ cm$^{-2}$ with excitation temperatures of 165 $\pm$ 21 K and 170 $\pm$ 32 K, respectively. The fractional abundances of NH$_{2}$CHO and HNCO toward G358.93$-$0.03 MM1 are (9.03$\pm$1.44)$\times$10$^{-10}$ and (5.80$\pm$2.09)$\times$10$^{-9}$. We compare the estimated abundances of NH$_{2}$CHO and HNCO with the existing three-phase warm-up chemical model abundance values and notice that the observed and modelled abundances are very close. We conclude that NH$_{2}$CHO is produced by the reaction of NH$_{2}$ and H$_{2}$CO in the gas phase toward G358.93$-$0.03 MM1. Likewise, HNCO is produced on the surface of grains by the reaction of NH and CO toward G358.93$-$0.03 MM1. We also find that NH$_{2}$CHO and HNCO are chemically linked toward G358.93$-$0.03 MM1.

astro-ph.GA↗

arXiv2024

Discovery of giant radio sources from TGSS ADR 1: radio, optical, and infrared properties

Giant radio sources (GRSs) are the single largest astrophysical objects known in the universe that have grown to megaparsec scales ($\ge$ 0.7 Mpc). GRSs are much rarer compared with normal-sized radio galaxies. Still, the reason for the formation of their gigantic sizes is under debate. We systematically search for GRSs from the TIFR GMRT Sky Survey Alternative Data Release 1 (TGSS ADR 1) at 150 MHz. We have newly identified 34 GRSs from this study. We have also studied the multi-wavelength properties (radio, optical, and infrared) of these GRSs. We have used the likelihood ratio method to identify highly reliable multi-wavelength counterparts of GRSs from Pan-STARRS (optical) and WISE (mid-IR) data. We have classified GRSs based on their accretion mode of the central black holes using optical and mid-IR data. For all sources, we also discuss the principal characteristic parameters (redshift distribution, angular and projected linear size, total integrated radio flux density, spectral index, and radio power). We show the radio evolution track and the location of the GRSs in the P-D diagram. Using a radio-optical luminosity diagram, we identify GRSs in the Fanaroff-Riley classification. Only two GRGs in our sample reside close to the centres of galaxy clusters.

astro-ph.GA↗

arXiv2024

Study of Complex Nitrogen and Oxygen-bearing Molecules toward the High-mass Protostar IRAS 18089$-$1732

The observation of oxygen (O)- and nitrogen (N)-bearing molecules gives an idea about the complex prebiotic chemistry in the interstellar medium (ISM). In this article, we present the identification of the rotational emission lines of N-bearing molecules ethyl cyanide (C$_{2}$H$_{5}$CN), cyanoacetylene (HC$_{3}$N), and O-bearing molecules methyl formate (CH$_{3}$OCHO) towards high-mass protostar IRAS 18089$-$1732 using the Atacama Compact Array (ACA). We also detected the emission lines of both N- and O-bearing molecule formamide (NH$_{2}$CHO) in the envelope of IRAS 18089$-$1732. We have detected the $v$ = 0 and 1 states rotational emission lines of CH$_{3}$OCHO. We also detected the two vibrationally excited states of HC$_{3}$N ($v$7 = 1 and $v$7 = 2). The estimated fractional abundances of C$_{2}$H$_{5}$CN, HC$_{3}$N ($v$7 = 1), HC$_{3}$N ($v$7 = 2), and NH$_{2}$CHO towards the IRAS 18089$-$1732 are (1.40$\pm$0.5)$\times$10$^{-10}$, (7.5$\pm$0.7)$\times$10$^{-11}$, (3.1$\pm$0.4)$\times$10$^{-11}$, and (6.25$\pm$0.82)$\times$10$^{-11}$. Similarly, the estimated fractional abundances of CH$_{3}$OCHO ($v$ = 0) and CH$_{3}$OCHO ($v$ = 1) are (1.90$\pm$0.9)$\times$10$^{-9}$ and (8.90$\pm$0.8)$\times$10$^{-10}$, respectively. We also created the integrated emission maps of the detected molecules, and the observed molecules may have originated from the extended envelope of the protostar. We show that C$_{2}$H$_{5}$CN and HC$_{3}$N are most probably formed via the subsequential hydrogenation of the CH$_{2}$CHCN and the reaction between C$_{2}$H$_{2}$ and CN on the grain surface of IRAS 18089$-$1732. We found that NH$_{2}$CHO is probably produced due to the reaction between NH$_{2}$ and H$_{2}$CO in the gas phase. Similarly, CH$_{3}$OCHO is possibly created via the reaction between radical CH$_{3}$O and radical HCO on the grain surface of IRAS 18089$-$1732.

astro-ph.GA↗

arXiv2024

Detection and prebiotic chemistry of possible glycine precursor molecule methylenimine towards the hot molecular core G10.47+0.03

Amino acids are essential for the synthesis of protein. Amino acids contain both amine (R$-$NH$_{2}$) and carboxylic acid (R$-$COOH) functional groups, which help to understand the possible formation mechanism of life in the universe. Among the 20 types of amino acids, glycine (NH$_{2}$CH$_{2}$COOH) is known as the simplest non-essential amino acid. In the last 40 years, all surveys of NH$_{2}$CH$_{2}$COOH in the interstellar medium, especially in the star-formation regions, have failed at the millimeter and sub-millimeter wavelengths. We aimed to identify the possible precursors of NH$_{2}$CH$_{2}$COOH, because it is highly challenging to identify NH$_{2}$CH$_{2}$COOH in the interstellar medium. Many laboratory experiments have suggested that methylenimine (CH$_{2}$NH) plays a key role as a possible precursor of NH$_{2}$CH$_{2}$COOH in the star-formation regions via the Strecker synthesis reaction. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we successfully identified the rotational emission lines of CH$_{2}$NH towards the hot molecular core G10.47+0.03 using the Atacama Compact Array (ACA). The estimated column density of CH$_{2}$NH towards G10.47+0.03 is (3.40$\pm$0.2)$\times$10$^{15}$ cm$^{-2}$ with a rotational temperature of 218.70$\pm$20 K, which is estimated from the rotational diagram. The fractional abundance of CH$_{2}$NH with respect to H$_{2}$ towards G10.47+0.03 is 2.61$\times$10$^{-8}$. We found that the derived abundance of CH$_{2}$NH agree fairly well with the existing two-phase warm-up chemical modelling abundance value of CH$_{2}$NH. We discuss the possible formation pathways of CH$_{2}$NH within the context of hot molecular cores, and we find that CH$_{2}$NH is likely mainly formed via neutral-neutral gas-phase reactions of CH$_{3}$ and NH radicals towards G10.47+0.03.

astro-ph.GA↗

arXiv2024

A horseshoe-shaped ring of diffuse emission detected at 1.4 GHz

We identify a horseshoe-shaped ring (HSR) of diffuse emission in J1407+0453 from the Faint Images of Radio Sky at Twenty-cm (FIRST) survey using the Very Large Array telescope. An optical galaxy SDSSJ140709.01+045302.1 is present near the limb of the HSR of J1407+0453, with a spectroscopic redshift of $z=0.13360$. The total extent of the source, including the diffuse emission of J1407+0453, is 65 arcsec (with a physical extent of 160 kpc), whereas the diameter of the HSR is approximately 10 arcsec (25 kpc). The flux density of HSR is $\sim$47 mJy at 1400 MHz whereas the flux densities of whole diffuse emission of J1407+0453 at 1400 MHz and 150 MHz are 172 mJy and 763 mJy, respectively. We measure the radio luminosity of HSR J1407+0453 as 1.94 $\times 10^{24}$ W Hz$^{-1}$ with a spectral index $α_{150}^{1400}=-0.67$. The black hole mass of J1407+0453 is 5.8$\times10^8$ M$_{\odot}$. We compare the HSR of diffuse emission of J1407+0453 with other discovered diffused circular sources. The possible formation scenarios for J1407+0453 are discussed to understand the nature of the source. We present a spectral index map of J1407+0453 to study the spectral properties of the source.

astro-ph.GA↗

arXiv2024

Tailed Radio Galaxies from the TIFR GMRT Sky Survey

We present a list of candidate tailed radio galaxies using the TIFR GMRT Sky Survey Alternative Data Release 1 (TGSS ADR1) at 150 MHz. We have visually examined 5336 image fields and found 264 candidates for the tailed galaxy. Tailed radio galaxies are classified as Wide Angle Tailed (WAT) galaxies and Narrow-Angle Tailed (NAT) galaxies, based on the angle between the two jets of the galaxy. We found a sample of tailed radio galaxies which includes 203 `WAT' and 61 `NAT' type sources. These newly identified tailed sources are significant additions to the list of known tailed radio galaxies. The source morphology and luminosity features of the different candidate galaxies and their optical identifications are presented in the paper. Other radio properties and general features of the sources are also discussed.

astro-ph.GA↗

arXiv2024

Search for X/Z-shaped radio sources from TGSS ADR 1

A small sub-class of radio galaxies that exhibit a pair of secondary low surface brightness radio lobes oriented at an angle to the primary high surface brightness lobes are known as X-shaped radio galaxies (XRGs). In cases, it is seen that the less luminous secondary lobes emerge from the edges of the primary high brightened lobes and give a Z-symmetric morphology. These are known as Z-shaped radio galaxies (ZRGs). From the TIFR GMRT Sky Survey at 150 MHz, we present a systematic search result for XRGs and ZRGs. We identified a total of 58 radio sources, out of which 40 are XRGs and 18 are ZRGs. Taking advantage of the large sample size of the XRGs and ZRGs reported in the current paper, different properties of XRGs and ZRGs are studied. Out of 58 XRGs and ZRGs presented in the current paper, 19 (32 per cent) are FR-I and 33 (57 per cent) are FR-II radio galaxies. For four XRGs and three ZRGs, the morphology is so complex that they could not be classified. We have estimated radio luminosity and spectral index of newly discovered winged radio galaxies and made a comparative study with previously detected XRGs and ZRGs. Most of the XRGs show a steep spectral index between 150 MHz and 1400 MHz and only 14 per cent of the sources show a flat spectrum but for ZRGs, a good fraction of the sources (36 per cent) show a flat spectrum.

astro-ph.GA↗

arXiv2024

Detection of possible glycine precursor molecule methylamine towards the hot molecular core G358.93$-$0.03 MM1

The search for the simplest amino acid, glycine (NH$_{2}$CH$_{2}$COOH), in the interstellar medium (ISM), has become a never-ending story for astrochemistry and astrophysics researchers because that molecule plays a possible connection between the Universe and the origin of life. In the last forty years, all searches for NH$_{2}$CH$_{2}$COOH in the ISM at millimeter and submillimeter wavelengths have failed. Since the detection of NH$_{2}$CH$_{2}$COOH in the ISM was extremely difficult, we aimed to search for the possible precursors of NH$_{2}$CH$_{2}$COOH. Earlier, many laboratory experiments have suggested that methylamine (CH$_{3}$NH$_{2}$) plays an important role in the ISM as a possible precursor of NH$_{2}$CH$_{2}$COOH. After spectral analysis using the local thermodynamic equilibrium (LTE) model, we identified the rotational emission lines of CH$_{3}$NH$_{2}$ towards the hot molecular core G358.93$-$0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The column density of CH$_{3}$NH$_{2}$ towards the G358.93$-$0.03 MM1 was estimated to be (1.10$\pm$0.31)$\times$10$^{17}$ cm$^{-2}$ with an excitation temperature of 180.8$\pm$25.5 K. The fractional abundance of CH$_{3}$NH$_{2}$ with respect to H$_{2}$ towards the G358.93$-$0.03 MM1 was (8.80$\pm$2.60)$\times$10$^{-8}$. The column density ratio of CH$_{3}$NH$_{2}$ and NH$_{2}$CN towards G358.93$-$0.03 MM1 was (1.86$\pm$0.95)$\times$10$^{2}$. The estimated fractional abundance of CH$_{3}$NH$_{2}$ towards the G358.93$-$0.03 MM1 agrees fairly well with the previous three-phase warm-up chemical modelling abundance of CH$_{3}$NH$_{2}$. We also discussed the possible formation mechanism of CH$_{3}$NH$_{2}$, and we find that CH$_{3}$NH$_{2}$ is most probably formed via the reactions of radical CH$_{3}$ and radical NH$_{2}$ on the grain surface of G358.93$-$0.03 MM1.

astro-ph.GA↗

arXiv2024

Multi-wavelength observation of MAXI J1348$-$630 during the outburst in 2019

We study the multi-wavelength spectral properties of the black hole X-ray binary MAXI J1348$-$630 using quasi-simultaneous $\textit{ALMA}$, $\textit{NICER}$, and $\textit{Swift}$ observations during the decay phase of the January 2019 outburst. In millimeter wavelengths, radio continuum emissions in the frequency range of 89.56$-$351.44~GHz are measured. We found that the flux densities at millimeter wavelength varied between 12.18 mJy and 18.47 mJy with spectral index ($α$) of $0.28\pm 0.02$. The broadband spectrum suggests that the source was accompanied by weak synchrotron emission from the compact jets. Broadband spectral study indicates that MAXI J1348--630 falls in the regime of ``radio-quiet'' during the decay phase of the outburst. The $\textit{NICER}$ spectrum is fitted by a combined model of disk blackbody component $(\textit{diskbb})$ along with a comptonization component $(\textit{simpl})$ which explains the power-law continuum caused by the thermal Comptonisation of soft disk photons in a hot gas of electrons. The $\textit{NICER}$ spectrum is dominated by the comptonised components during the decay phase of the outburst close to the hard state of the source. We have investigated the correlation between X-ray and radio luminosity using quasi-simultaneous $\textit{ALMA}$ and $\textit{NICER}$ data to understand the source nature by locating the source in the $L_{X}$-$L_{R}$ diagram. The correlation study of radio/X-ray luminosity suggests that MAXI J1348--630 did not follow the well-known track for black holes and it is a new member of a restricted group of sources.

astro-ph.HE↗

arXiv2024

Detection and chemical modelling of complex prebiotic molecule cyanamide in the hot molecular core G31.41+0.31

In the interstellar medium (ISM), the complex prebiotic molecule cyanamide (NH$_{2}$CN) plays a key role in producing adenine (C$_{5}$H$_{5}$N$_{5}$), purines (C$_{5}$H$_{4}$N$_{4}$), pyrimidines (C$_{4}$H$_{4}$N$_{2}$), and other biomolecules via a series of reactions. Therefore, studying the emission lines of NH$_{2}$CN is important for understanding the hypothesis of the pre-solar origin of life in the universe. We present the detection of the rotational emission lines of NH$_{2}$CN with vibrational states $v$ = 0 and 1 towards the hot molecular core G31.41+0.31 using the high-resolution twelve-meter array of Atacama Large Millimeter/Submillimeter Array (ALMA) band 3. The estimated column density of NH$_{2}$CN towards G31.41+0.31 using the local thermodynamic equilibrium (LTE) model is (7.21$\pm$0.25)$\times$10$^{15}$ cm$^{-2}$ with an excitation temperature of 250$\pm$25 K. The abundance of NH$_{2}$CN with respect to H$_{2}$ towards G31.41+0.31 is (7.21$\pm$1.46)$\times$10$^{-10}$. The NH$_{2}$CN and NH$_{2}$CHO column density ratio towards G31.41+0.31 is 0.13$\pm$0.02. We compare the estimated abundance of NH$_{2}$CN with that of other hot cores and corinos and observed that the abundance of NH$_{2}$CN towards G31.41+0.31 is nearly similar to that of the hot molecular core G358.93$-$0.03 MM1, the hot corinos IRAS 16293-2422 B, and NGC 1333 IRAS4A2. We compute the two-phase warm-up chemical model of NH$_{2}$CN using the gas-grain chemical code UCLCHEM, and after chemical modelling, we notice that the observed and modelled abundances are nearly similar. After chemical modelling, we conclude that the neutral-neutral reaction between NH$_{2}$ and CN is responsible for the production of NH$_{2}$CN on the grain surface of G31.41+0.31.

astro-ph.GA↗

arXiv2023

ACA observation and chemical modelling of phosphorus nitride (PN) towards the hot molecular cores G10.47+0.03 and G31.41+0.31

Phosphorus (P) is one of the important elements for the formation of life and plays a crucial role in several biochemical processes. Recent spectral line surveys have confirmed the existence of P-bearing molecules, especially PN and PO, in the star-formation regions, but their formation mechanisms are poorly understood. The P-bearing molecule phosphorus nitride (PN) is detected in several star-forming regions, but this molecule has been poorly studied at high gas densities ($\geq$10$^{6}$ cm$^{-3}$) hot molecular cores. In this article, we present the detection of the rotational emission line of PN with transition J = 3$-$2 towards the hot molecular cores G10.47+0.03 and G31.41+0.31, using the Atacama Compact Array (ACA). The estimated column densities of PN for G10.47+0.03 and G31.41+0.31 using the local thermodynamic equilibrium (LTE) model are (3.60$\pm$0.2)$\times$10$^{13}$ cm$^{-2}$ and (9.10$\pm$0.1)$\times$10$^{12}$ cm$^{-2}$ with an excitation temperature of 150$\pm$25 K. The fractional abundance of PN relative to H$_{2}$ is 2.76$\times$10$^{-10}$ for G10.47+0.03 and 5.68$\times$10$^{-11}$ for G31.41+0.031. We compute the two-phase warm-up chemical model of PN to understand the chemical evolution in the environment of hot molecular cores. After chemical modelling, we claim that PN is created in the gas phase via the neutral-neutral reaction between PO and N in the warm-up stage. Similarly, PN is destroyed via the ion-neutral reaction between H$_{3}$O$^{+}$ and PN.

astro-ph.GA↗