pyTANSPEC: A Data Reduction Package for TANSPEC

The TIFR-ARIES Near Infrared Spectrometer (TANSPEC) instrument provides simultaneous wavelength coverage from 0.55 to 2.5 micron, mounted on India's largest ground-based telescope, 3.6-m Devasthal Optical Telescope at Nainital, India. The TANSPEC offers three modes of observations, imaging with various filters, spectroscopy in the low-resolution prism mode with derived R~ 100-400 and the high-resolution cross-dispersed mode (XD-mode) with derived median R~ 2750 for a slit of width 0.5 arcsec. In the XD-mode, ten cross-dispersed orders are packed in the 2048 x 2048 pixels detector to cover the full wavelength regime. As the XD-mode is most utilized as well as for consistent data reduction for all orders and to reduce data reduction time, a dedicated pipeline is at the need. In this paper, we present the code for the TANSPEC XD-mode data reduction, its workflow, input/output files, and a showcase of its implementation on a particular dataset. This publicly available pipeline pyTANSPEC is fully developed in Python and includes nominal human intervention only for the quality assurance of the reduced data. Two customized configuration files are used to guide the data reduction. The pipeline creates a log file for all the fits files in a given data directory from its header, identifies correct frames (science, continuum and calibration lamps) based on the user input, and offers an option to the user for eyeballing and accepting/removing of the frames, does the cleaning of raw science frames and yields final wavelength calibrated spectra of all orders simultaneously.Comment: 10 pages, 6 figures, accepted for publication in the Special Issue of Journal of Astrophysics & Astronomy, 2022, Star formation studies in context of NIR instruments on 3.6m DOT, held at ARIES, Nainital during 4-7, May, 202

Quiescence of an Outburst of a Low-Mass Young Stellar Object: LDN1415-IRS

LDN1415-IRS, a low-mass young stellar object (YSO) went into an outburst between 2001 and 2006, illuminating a surrounding nebula, LDN1415-Neb. LDN1415-Neb was found to have brightened by I=3.77 mag by April 2006. The optical light curve covering $\sim$ 15.5 years, starting from October 2006 to January 2022, is presented in this study. The initial optical spectrum indicated the presence of winds in the system but the subsequent spectra have no wind indicators. The declining light curve and the absence of the P-Cygni profile in later epoch spectra indicate that the star and nebula system is retrieving back from its outburst state. Two Herbig-Haro objects (HHOs) are positioned linearly with respect to the optical brightness peak of the nebula, probably indicating the circumstellar disk being viewed edge-on. Our recent deep near-infrared (NIR) imaging using TANSPEC has revealed the presence of a nearby star-like source, south of the LDN1415-IRS, at an angular distance of $\sim$ 5.4 arcsec.Comment: Accepted for publication in the Journal of Astrophysics and Astronom

Improving the Thermal Stability of a CCD Through Clocking

Modern precise radial velocity spectrometers are designed to infer the existence of planets orbiting other stars by measuring few-nm shifts in the positions of stellar spectral lines recorded at high spectral resolution on a large-area digital detector. While the spectrometer may be highly stabilized in terms of temperature, the detector itself may undergo changes in temperature during readout that are an order of magnitude or more larger than the other opto-mechanical components within the instrument. These variations in detector temperature can translate directly into systematic measurement errors. We explore a technique for reducing the amplitude of CCD temperature variations by shuffling charge within a pixel in the parallel direction during integration. We find that this "dither clocking" mode greatly reduces temperature variations in the CCDs being tested for the NEID spectrometer. We investigate several potential negative effects this clocking scheme could have on the underlying spectral data.Comment: Submitted to JATIS, special issue from the ISPA 2018 conference. 11 pages, 9 figure

Constrained modelling of instrumental radial velocity drift in precision Radial Velocity Spectrometers: Application to HPF

For precise measurement of the radial velocity change in a star, the precision of the wavelength solution is 4 orders more important than accuracy of the wavelength solution. Since the absolute wavelength solution model of a multi-order echelle spectrographs require a large number of parameters, it is better to track the change in wavelength solution over time instead of refitting the complete wavelength solution without any constrains. For stabilized spectrographs like The Habitable-Zone Planet Finder (HPF) and NEID, these changes in wavelength solution are significantly low order and can be modeled with only a few parameters. Table 1, shows an example of low order changes to dispersion solution we expect from various physical mechanisms in HPF or NEID

Evidence for He I 10830 \AA~ absorption during the transit of a warm Neptune around the M-dwarf GJ 3470 with the Habitable-zone Planet Finder

Understanding the dynamics and kinematics of out-flowing atmospheres of hot and warm exoplanets is crucial to understanding the origins and evolutionary history of the exoplanets near the evaporation desert. Recently, ground based measurements of the meta-stable Helium atom's resonant absorption at 10830 \AA~has become a powerful probe of the base environment which is driving the outflow of exoplanet atmospheres. We report evidence for the He I 10830 \AA~in absorption (equivalent width $\sim$ $0.012 \pm 0.002$ \AA) in the exosphere of a warm Neptune orbiting the M-dwarf GJ 3470, during three transits using the Habitable Zone Planet Finder (HPF) near infrared spectrograph. This marks the first reported evidence for He I 10830 \AA\, atmospheric absorption for a planet orbiting an M-dwarf. Our detected absorption is broad and its blueshifted wing extends to -36 km/sec, the largest reported in the literature to date. We modelled the state of Helium atoms in the exosphere of GJ3470b based on assumptions on the UV and X-ray flux of GJ 3470, and found our measurement of flux-weighted column density of meta-stable state Helium $(N_{He^2_3S} = 2.4 \times 10^{10} \mathrm{cm^{-2}})$, derived from our transit observations, to be consistent with model, within its uncertainties. The methodology developed here will be useful to study and constrain the atmospheric outflow models of other exoplanets like GJ 3470b which are near the edge of the evaporation desert.Comment: Accepted in Ap

Impact of crosshatch patterns in H2RGs on high-precision radial velocity measurements: exploration of measurement and mitigation paths with the Habitable-Zone Planet Finder

Teledyne’s H2RG detector images suffer from crosshatch like patterns, which arise from subpixel quantum efficiency (QE) variation. We present our measurements of this subpixel QE variation in the Habitable-Zone Planet Finder’s H2RG detector. We present a simple model to estimate the impact of subpixel QE variations on the radial velocity and how a first-order correction can be implemented to correct for the artifact in the spectrum. We also present how the HPF’s future upgraded laser frequency comb will enable us to implement this correction

The Epoch of Giant Planet Migration Planet Search Program. I. Near-Infrared Radial Velocity Jitter of Young Sun-like Stars

We present early results from the Epoch of Giant Planet Migration program, a precise RV survey of over one hundred intermediate-age ($\sim$20$-$200 Myr) G and K dwarfs with the Habitable-Zone Planet Finder spectrograph (HPF) at McDonald Observatory's Hobby-Eberly Telescope (HET). The goals of this program are to determine the timescale and dominant physical mechanism of giant planet migration interior to the water ice line of Sun-like stars. Here, we summarize results from the first 14 months of this program, with a focus on our custom RV pipeline for HPF, a measurement of the intrinsic near-infrared RV activity of young Solar analogs, and modeling the underlying population-level distribution of stellar jitter. We demonstrate on-sky stability at the sub-2 m s$^{-1}$ level for the K2 standard HD 3765 using a least-squares matching method to extract precise RVs. Based on a subsample of 29 stars with at least three RV measurements from our program, we find a median RMS level of 34 m s$^{-1}$. This is nearly a factor of 2 lower than the median RMS level in the optical of 60 m s$^{-1}$ for a comparison sample with similar ages and spectral types as our targets. The observed near-infrared jitter measurements for this subsample are well reproduced with a log-normal parent distribution with $\mu=4.15$ and $\sigma=1.02$. Finally, by compiling RMS values from previous planet search programs, we show that near-infrared jitter for G and K dwarfs generally decays with age in a similar fashion to optical wavelengths, albeit with a shallower slope and lower overall values for ages $\lesssim$1 Gyr

Solar Contamination in Extreme-precision Radial-velocity Measurements: Deleterious Effects and Prospects for Mitigation

Solar contamination, due to moonlight and atmospheric scattering of sunlight, can cause systematic errors in stellar radial velocity (RV) measurements that significantly detract from the ~10 cm s−1 sensitivity required for the detection and characterization of terrestrial exoplanets in or near habitable zones of Sun-like stars. The addition of low-level spectral contamination at variable effective velocity offsets introduces systematic noise when measuring velocities using classical mask-based or template-based cross-correlation techniques. Here we present simulations estimating the range of RV measurement error induced by uncorrected scattered sunlight contamination. We explore potential correction techniques, using both simultaneous spectrometer sky fibers and broadband imaging via coherent fiber imaging bundles, that could reliably reduce this source of error to below the photon-noise limit of typical stellar observations. We discuss the limitations of these simulations, the underlying assumptions, and mitigation mechanisms. We also present and discuss the components designed and built into the NEID (NN-EXPLORE Exoplanet Investigations with Doppler spectroscopy) precision RV instrument for the WIYN 3.5 m telescope, to serve as an ongoing resource for the community to explore and evaluate correction techniques. We emphasize that while "bright time" has been traditionally adequate for RV science, the goal of 10 cm s−1 precision on the most interesting exoplanetary systems may necessitate access to darker skies for these next-generation instruments

Impact of crosshatch patterns in H2RGs on high-precision radial velocity measurements: exploration of measurement and mitigation paths with the Habitable-Zone Planet Finder

Teledyne’s H2RG detector images suffer from crosshatch like patterns, which arise from subpixel quantum efficiency (QE) variation. We present our measurements of this subpixel QE variation in the Habitable-Zone Planet Finder’s H2RG detector. We present a simple model to estimate the impact of subpixel QE variations on the radial velocity and how a first-order correction can be implemented to correct for the artifact in the spectrum. We also present how the HPF’s future upgraded laser frequency comb will enable us to implement this correction