K. Khushbu | Searcharxiv

arXiv2026

A Quiet Host in an Active Planet-Forming Disk: Optical Spectroscopy of WISPIT 2

WISPIT 2 is a young pre-main-sequence star hosting a multi-ringed transition disk and two directly imaged protoplanets, including the accreting WISPIT 2b, making it the closest known analogue to PDS 70. We present the first optical spectrum of its central star, obtained with HFOSC on the 2-m Himalayan Chandra Telescope, and derive its atmospheric parameters, test its youth, and constrain its accretion state. We analyse low-resolution spectra with iSpec and validate the pipeline at HFOSC resolution against Gaia FGK Benchmark Stars and K-type pre-main-sequence templates. We measure T_eff = 4551 +/- 150 K, log g = 4.32 +/- 0.18, and a low-resolution, model-dependent global metallicity [M/H] = -0.17 +/- 0.16. The surface gravity and Li I equivalent width support the pre-main-sequence nature of the host. H-alpha remains in net absorption but is partially filled by weak emission at only 1.5-2.0 sigma, approximately 1.1 dex below the expected chromospheric-noise level and therefore consistent with chromospheric activity rather than detectable accretion. We place a 95% upper limit on the stellar accretion rate of 3.6 x 10^-11 solar masses per year, below even the lowest monitored value for PDS 70 and implying a host-to-planet accretion-rate ratio below approximately 18. Both known double-protoplanet hosts therefore show strongly suppressed or undetectable stellar accretion. Larger spectroscopic samples are needed to determine whether this is common in multi-protoplanet transition disks.

astro-ph.SR↗

arXiv2024

Infrared properties of Planetary Nebulae with PG1159 central stars

We study the properties of 26 PNe with PG1159-type central stars known till date and compare them with the properties of PNe having [WR], $wels$ and hydrogen-rich central stars published earlier. We use archival photometric measurements of $2MASS$ for near-IR analysis and $WISE$ and $IRAS$ data for mid- and far-IR analysis and derive the IR properties of PG1159-PNe. We analyze the IR colour-colour diagrams of PG1159-PNe and compare them with the other three groups of PNe. Similar to the [WR]-PNe, many PG1159-PNe also show large amount of near-IR emission from the hot-dust component but their AGB dust is relatively cooler. We also report here the dust colour temperatures, dust masses, dust-to-gas mass ratios, IR luminosities and IR excess of PG1159-PNe and plot them against their surface H$\beta$ brightness (age) and compare them with the distribution of other groups of PNe. The IR luminosity and dust temperature show strong correlation with surface H$\beta$ brightness, however, the dust-to-gas mass ratio and IR excess do not show any trend. While the mean dust mass has a lower value for PG1159-PNe, in compared to other groups, the average dust-to-gas mass ratio is found to be marginally larger for PG1159-PNe. An analysis of the number distribution of different groups of PNe against surface H$\beta$ brightness shows that a) younger [WR]-, $wels$- and normal-PNe have a similar distribution indicating that they all have evolved from the AGB in a similar way, b) while there is an overlap of surface H$\beta$ brightness between [WR]- and PG1159-PNe, showing an evolutionary connection between them, there exists a significant gap between the values derived for $wels$- and PG1159-PNe.

astro-ph.SR↗